Method of preventing scum and efflorescence on brick and clay ware



Patentedsept. 20, 1932 A CORPORATION" OF DELAWARE JAMES PIERCE, JR., AND ROBERT CURNES, OF CHARLESTON, WEST VIRGINIA, AS-

SIGNORS TO BARIUM REDUCTION CORPORATION, OF CHARLESTON, WEST VIRGINIA,

METHOD OF PREVENTING SCUM AND EFFLORESCENCE ON BRICK AND CLAY WARE v No Drawing.

This invention relates to the prevention of scum, i. e., the coating which develops on the surface of brick and clay wares during drying or burning the same, and also the prevention of efliorescence on the same materials, i. e. the coating which develops on the surfacethereof after removal of the same from the kiln and most generally after the materials have been set up in a wall and subjected to weathering conditions and WlllCh coatings are usually due to the formation of alkali-metal or alkaline-earth sulphates, and more commonly calcium sulphate which migrate to the surface of such materials.

It has heretofore been proposed to employ barium carbonate and other compounds of barium, more particularly barium sulphide and chloride, toprevent theformation ofscum and effiorescence in brick and other ceramic products, reference being had in this connection to the Patent No. 1,583,903 and also to an article by Ellis Lovejoy, Transactions of the American Ceramic Society 1908,

Vol. VIII. p. 255265 entitled, The use of barium compounds in preventing scum, as well as in the trade pamphlet bythe same author dated 1927, in which articles Lovejoy as early 'as 1908 suggested the use of barium bi-carbonate and pointed outmany of its s theoretical advantages, without however, de-

scribing the procedure by which barium bicarbonate could be utilized in order to realize suchadvantages; In a later article, 1927, Lovejoy, while still featuring the theoretical advantages of employingbarium bi-carbonate for the above mentioned purposes, fails to outline a practical and feasible procedure of applying the same in the usual commercial the carbonate with charcoal, oreby passing the combustion gases from a non-sulphurous fuel through a slurry of the carbonate. It

is not stable and cannot be produced and marketed because it rapidly" oxidizes and re turns to the less solublecarbonate form. Be-

Application filed September 22, 1930. Serial No. 483,749.

cause of its unstable character little is known about it, but it proved effective in the worst instance of scum we have ever experienced,- a brick made from a mixture of clay and coal ash. Barium lei-carbonate would not be open to the objections of the other soluble barium salts in that it likely is less soluble and in that it soon returns to thecarbonate. With proper'equipment it would be a simple and safe method of increasing. the activity of the carbonate if need be.

Again, with reference to the efiiorescence,

he states:

Our first thought is to use some form of barium salt for the corrective. For treatment of burned clay wares we must use clear solutions. Barium carbonate is not sufficiently soluble and we have not the advantage of reactivity as in treating scum. The bicarbonate will give us a stronger solution and we can precipitate the sulphur radical in the efllorescence and make it insoluble, but we leave soluble carbonates,.except in the case of magnesiumand calcium. Where the of .fiorescence consists largely of magnesium and I calcium, we may expect results from the use of barium bi-carbonate. The barium chloride, fluoride and hydrate would themselves efiioresce when in excess and we can have no measure of the quantity touse. -Moreover, except in the case of the barium sulphate precipitate, thereactions produce soluble salts.

It willbe noted Lovejoy carried on no investigation as to the conversion of normal carbonate to bi -carbonate. His statement that [it can be produced by passing pure. CO

gas through a suspension in water is entirely an abstract or theoretical speculation not operable insofar as scum prevention in a a practice is concerned, as there is never sufficient water added at the pug mill to permit of complete conversion of all the normal carbonate to bi-carbonate that is required for scum prevention.

Also, his statement that the bi-carbonate .would be more useful for preventing efliorescence than the normal carbonate is totally erroneous,as there can be no bi-carbonate in the brick. after even drying at 110 C. or higher. and certainly not after burning at 100 0 C. or better. Bi-carbonate does prevent efllorescence better than normal carbonate because the normal carbonate resulting from the breaking down of the bi-carbonate in drying or burning is in a much more finely clivided state and much more evenly and uniformly distributed throughout the mass of the brick-or clay wares treated.

Our investigations have led to the discovery of a wholly practical and feasible procedure for theprevention of scum and ef- 7florescencej upon brick and other ceramics whereby scum formation and eiflorescence is economically and eifectivelyprevented or eliminated.- 'In carrying out our invention, we preferably proceed as follows e When normal barium carbonate is employed, it is common practice to use. a 25 to 50% excess over that theoretically required to precipitate all the soluble sulphates in the clay, this large excess being necessary due to the insolubility and consequent impossibility of the reaction 'nacosrasoi aooeeasor proceeding 1 to completion in the time and under the conditionspertainingin the manufacture of brick and ceramic ware.

If barium bi-carbonate could be substituted in whole for the barium carbonate it would react instantly in the above reaction just as any other soluble barium salt would, but this 'is not feasible since there is always present a greater amount of soluble sulphates than is "required to satisfy the barium bi-carbonate formed in the amount of water usedto pug the clay. I We'have,.however, discovered that if only as little as 20% .of-thecarbonate required to theoretically combine with the sulphate is present .as bi-carbonate that all the advantages are to be had just the same "asxif the theoretical amount of'barium was present as bicarbonate. Tobring this about we proceed as follows:

A determination-ofthe S content of the clay which is utilized in the manufacture of the brick and the water used pugging is 'made and based. on this determination the viously carefully scrubbed, first with water to remove soot and entrained ash and then with a weak suspension of barium carbonate 1n water .to remove sulphur dioxide, are then ".causedjto pass into the mixture of "barium carbonate suspended in the Wateras afore- 'Organic Substances).

at 1 O.to -C.,-w-h-ich reaction is ,represented by the following equation After equilibriumhas been reached under the above conditions of temperature and pressure, it will be found that a solution of 'Ba ('HCO in water exists approximating 0.24% or, in terms of BaCO 0.18% i. e. from to of'the barium carbonate in the original suspension has been converted to bicarbonate and passed into solution. For inv stance, if the clayrequired five pounds of BaCO3 per thousand brick, the 7 50 pounds of water would contain 0.18% BaCO or 1.35 pounds which would be 27% of the -5 pounds originally in suspension.

.This mixture of'bi-carbonate in solution and carbonate in suspension is now mixed with the clayat the pug mill, when the following reactions take place:

(Note 4) -.(Note'5) (Note) (Note 6) 1-Soluble 1 part -in 500 water at 18 C. V 2Soluble 1 part in 450 water at 15 C.

i and 0 partial pressure C0 7 I 3 -Soluble 1 part in-432,000 water at19 4'-Soluble 1 part in.2,600 water at 15 and 0 partial pressure CO I 5Soluble;1'part in 45,500water at 18 .'6Soluble 1 part in"89,000 water at 20 Above 'solubilities, except that of from Seidells Solubilities'of Inorganic and The above noted reactions are equally applicable to all sulphates of the alkali and alkaline-earth metals.

The barium lei-carbonate acts cyclically as explained inureac'tions on page 5 ante, since the small portion thereof first reacts with a portion of the calcium; sulphate to form calcium, bi-carbonate which, in turn reacts with the barium carbonate to form another portion of barium bi-carbonate, whereupon the cycle ofqreaction is repeated. As a consequence, notwithstanding the fact that the amountofbariumbi-carbonate may be far less than that which will be required tosatisfy all of the calcium sulphate and sulphuric acid present in the pugging mill, the net result of the cycle of reactions of both the barium carbonate and barium bi-carbonate are brought into actionthrough this barium bi-carbonate catalyzer.

To substantiate theoretically our foregoing Calcium sulphate:

Concentration: 0.002086 gins. CaSOi per cc. equivalent to 0003024- gins. 100% BaCO ggg i g tfi Per centre- Per cent is Per cent rethememal acted with acted with acted with 35 i of theoretical theoretical air with- Time 27 0 er amount 7 amount air etite same minutes i g barium carfloated weight as bonqte; bonate (98.0 Witherite theoretical corbzmate per cent (87.56 per barium carsfispension BaCOa) cent BaCOs) bonate Magnesium sulphate Concentration: 0.001823 gms. MgSO cc.

equiv. to 0.002989 gms. BaOO 100% Per cent re- Per cent re- Per cent re- Per cent reififi g acted with acted with acted with mount theoretical theoretical air With- 40 Time 97 0 er amount amount air erito same minutes i barium carfloated weight as bonatk bonate (98.0 witherite theoretical carbonate per cent (87.56 per barium carsuspension B21003) cent BaCO bonate Sodium suZphate:

Concentration 0.002199 gms. Na SO cc. equlv. to 0.003056 gins. 100% BaCO Per cent re- Per cent re Per cent re- Per cent re- ?figiggggfi acted with acted with acted with amount of theoretical theoretical air with- 'l ime 97 0 er amount amount air erite same minutes 3 g barium carfloated weight as bonatk bonate (98.0 witherite theoretical carbonate per cent (87.56 per barium carsuspensiofi BaCO cent B21003) bonate 15 95 5 38.4 22 9 21.4 30 9G 0 52.2 .6 4 2i. 2 n 95 2 66.2 31 4 29.1

From these tests it can be seen that the reactivity of a 27.0% bicarbonate suspension 18 practlcally that of a soluble barium salt,

i. e. 100%, and that we have evolved a process process. 7 I, Theexpression pugglng as used in the appended claims refersto the well known 7 for making the normal barium carbonate practically 100%: reactiveffor the prevention of scum and efliorescence in brick and clay wares generally. j p l I Although we preferably convert but about 20%130' 30% of the barium carbonate into bicarbonate, nevertheless without departing from the spirit of my invention up toap proximately 60% of the barium carbonate introduced in suspension can be converted into barium bicarbonatm'but as explained ante, unless the barium carbonate is converted in part into barium bicarbonate,the desired cyclic reaction cannot occur and a very incomplete conversion of the soluble sulphates into insoluble barium sulphate is accomplished. Whilewe prefer to employ sub}- stantially purekilngases for the conversion of the barium carbonate into bicarbonate, we do not limit ourselvesthereto, as carbon Vdioxide gas substantially freefrom deleterious ingredients can be employed injlieu thereof, if desired, and wherever the activesubstantially pure carbon dioxide isemployed in the claims, we refer to carbon dioxide free from impurities which would be del'eterious to accomplishing the desired Fobjects ofv 1 this practice of incorporating clayw'ith water .prior to the shaping of the same to the desired form. t

Various changes and proportions of the ingredients employedand in the procedure,

within the scope of the appended claims may be madewithout departing from the spirit ofour invention. 7 j

Having thus described our invention what stateslLettersaPatent is 1. The methodof treatingclay to prevent scum formation and eiilorescence subsequent to the firingthereof in" the manufacture of brick or clay wares. which comprises passing a gas containing 00 'as, at a pressure notexceeding atmospheric pressure, through a suspension of barium carbonate, the amount We Qclaim and desireto obtain by United of the barium radical in such carbonate being substantially sufficientto combine with the SO radical of the water soluble sulphates in a batch of clay to be pugged and the amount of CO gas reacting with thebarium car-1 bonate being sufficient to but partially convert the barium carbonate in suspension into soluble barium bicarbonate, pugging the batch of clay with the aqueous mixture so obtained and allowing the reaction therein to proceed until substantially all of the soluble sulphates in the mixture react with the barium bicarbonate formed therein to produce precipitated barium sulphate.

2. The method of treating clay to prevent scum formation and efiorescence subsequent to the firing thereof in the manufacture of brick orIclay wares, which comprises passing a. gas containing CO gas,at'a pressure not exceeding atmospheric pressure, through a suspension of barium carbonate, the amount ofthe barium radical in such carbonate'being substantially sufiicient to combine with the S0 radical of the water soluble'sulph'ates ina batch of .clay to be pugged and "the-A amount of CO gas reacting with the barium d carbonate being sufiicient to'convert'but a portion, not exceeding 60%, of the barium carbonate in suspension, into thesoluble barium bicarbonate, pugging the batch of clay to be pugged with the aqueous mixture so obtained and allowing the reaction therein to proceed. until substantially all of the soluble sulphates in the mixture react with the barium bicarbonate formed therein to produce precipitated barium sulphate.

The' method oftreating clay to prevent scum formation and efflorescence subsequent to the firing-thereof in the manufacture of brick or clay Wares, which comprises passing I a gas containing CO gas, at atmospheric pressure through suspension of barium car-' bo'nate, the amount of the bariumradical in such carbonate being substantially suflicient to combine the S0 radical of the water soluble sulphates in a batch of clay to be pugged and the'amount of CO gas reacting with the barium carbonate being sufficient to convert a minor portion, between '2l0% and 30%, of the barium carbonate insuspension into soluble. barium bicarbonate, pugging the batch of clay' with the aqueous mixture so obtained and allowing the reaction thereinto proceed until-substantially all of the soluble sulphates in the mixture react, with the barium bicarbonate formed therein to produce precipitated barium sulphate I 40 Signed at Charleston in the county of Kanawah and State ofWest Virginia, this" 15th day of September, c1930.

' JAMES B. PIERCE, .JR. ROBERT L. CURNES. 

